JP2002294171A - Process for producing powder coating material composition excellent in stain resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for producing a powder coating material composition which is excellent in stain resistance and makes it possible to sufficiently disperse a silicate compound in a binder resin. SOLUTION: In the process for producing the powder coating material composition excellent in stain resistance by melting and kneading a raw material comprising the binder resin, a curing agent and the silicate compound, the melting and kneading are repeatedly performed two or more times.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a powder coating, and more particularly to a method for producing a powder coating composition having excellent stain resistance.

[0002]

2. Description of the Related Art It is well known that the addition of a silicate compound to a solvent-based paint can impart stain resistance to the resulting coating film. This is considered to be because the silicate compound is hydrolyzed after transferring to the surface, thereby enhancing the hydrophilicity of the surface.

[0003] In general, powder coatings are prepared by heating raw materials such as a premixed binder resin and a curing agent into a viscous material having a very high viscosity.
It is manufactured by grinding. When a method using melt kneading is used to add a silicate compound to a clear powder coating, the resulting coating film may become cloudy. This is thought to be due to the fact that the silicate compound is in a liquid state, and is not sufficiently kneaded into the binder resin, which is a main component of the raw material, during the melt-kneading, and is not well dispersed in the powder coating particles. Can be

[0004] On the other hand, in the premix before melt-kneading, the silicate compound is adsorbed on the pigment surface and its function is substantially inactivated, so that the stain resistant function is not imparted to the coating film. Sometimes.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a powder coating composition which is capable of sufficiently dispersing a silicate compound in a binder resin and has excellent stain resistance. It is.

[0006]

According to the present invention, there is provided a method for producing a powder coating composition having excellent stain resistance, which comprises melting and kneading a raw material comprising a binder resin, a curing agent, and a silicate compound. In the method for producing a product, the melt kneading is performed twice or more. Here, the raw material may further contain a pigment. Another method for producing a powder coating composition having excellent stain resistance according to the present invention is a method wherein the silicate compound is deactivated to a component obtained by melt-kneading a first raw material comprising a binder resin and a silicate compound. And melting and kneading by adding a second raw material containing the following components. Here, the deactivating component may be a pigment. The powder coating composition excellent in stain resistance of the present invention is obtained by the above-mentioned production method.
The method for forming a coating film having excellent stain resistance according to the present invention is to apply and bake the above powder coating composition.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The first method for producing a powder coating composition according to the present invention is characterized by melting and kneading a raw material twice or more. This raw material is a binder resin,
It is composed of a curing agent and a silicate compound.

Examples of the binder resin and the curing agent include those commonly used for powder coatings. As the binder resin, a polyester resin, an epoxy resin, or an acrylic resin having a functional group capable of reacting with a curing agent is generally used. Further, these can be appropriately blended and used as a polyester / epoxy resin, an acryl / epoxy resin, or an acryl / polyester resin.

The above polyester resin can be obtained by polycondensation using an acid component containing a polyhydric carboxylic acid as a main component and an alcohol component containing a polyhydric alcohol as a main component by a usual method. it can. The acid component is not particularly limited, and examples thereof include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid and anhydrides thereof, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, and the like. , Succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, saturated aliphatic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, and their anhydrides, lactones such as γ-butyrolactone and ε-caprolactone. And aromatic oxymonocarboxylic acids such as p-oxyethoxybenzoic acid, and corresponding hydroxycarboxylic acids and the like.

The alcohol component is not particularly restricted but includes, for example, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,5-hexanediol and diethylene glycol. , Triethylene glycol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, bisphenol A alkylene oxide adduct, bisphenol S alkylene oxide adduct, 1,2-propanediol, neopentyl glycol, 1,2-butane Diol, 1,3-butanediol, 1,2-pentanediol, 2,3-pentanediol, 1,4-pentanediol, 1,4-hexanediol, 2,5-
Aliphatic glycols having a side chain such as hexanediol, 3-methyl-1,5-pentanediol, 1,2-dodecanediol, and 1,2-octadecanediol; trivalent such as trimethylolpropane, glycerin and pentaerythritol The above polyhydric alcohols and the like can be exemplified.

By controlling the types and amounts of the compounds contained in the acid component and the alcohol component, a polyester resin having a predetermined amount of a functional group capable of reacting with a curing agent can be obtained. In addition, when the acid component contains 50% by weight or more, preferably 80% by weight or more of isophthalic acid, a polyester resin having high weather resistance can be obtained.

The above acrylic resin can be obtained by blending an ethylenically unsaturated group-containing monomer and copolymerizing the same with a usual method. Examples of the ethylenically unsaturated group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl acrylate, Praxel FM and FA series (trade name, 2-hydroxyethyl Adduct of (meth) acrylate and polycaprolactone, manufactured by Daicel Chemical Industries, Ltd.)
Hydroxyl-containing monomers such as polyalkylene glycol mono (meth) acrylates, glycidyl acrylate,
Epoxy group-containing monomers such as glycidyl methacrylate and 2-methylglycidyl methacrylate; amino group-containing monomers such as dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate;
(Meth) acrylamide, N-methyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide,
Acrylamide monomers such as N-methylacrylamide, curing functional group-containing monomers such as carboxylic acid group-containing monomers such as (meth) acrylic acid, and acrylonitrile, vinyl acetate, methyl (meth) acrylate, and ethyl (meth) acrylate , N-butyl (meth) acrylate, iso-butyl (meth) acrylate, tert-butyl (meth) acrylate, styrene, vinyltoluene,
Other neutral monomers such as p-chlorostyrene can be exemplified. By appropriately blending these ethylenically unsaturated group-containing monomers, an acrylic resin having a predetermined amount of a functional group capable of reacting with a curing agent can be obtained.

Further, the epoxy resin is a compound having an epoxy group as a functional group capable of reacting with two or more curing agents in one molecule, for example, a glycidyl ester resin, bisphenol A and epichlorohydrin. Glycidyl ether type resins such as a condensation reaction product with phosphorus and a condensation reaction product of bisphenol F with epichlorohydrin,
Examples thereof include alicyclic epoxy resins, aliphatic epoxy resins, bromide-containing epoxy resins, phenol novolak epoxy resins, and cresol novolak epoxy resins.

On the other hand, when the functional group of the binder resin is a hydroxyl group, the curing agent is an aliphatic polycarboxylic acid,
An aliphatic acid anhydride, an amino resin, a polyepoxy compound, a blocked isocyanate compound, a glycoluril curing agent and the like are used. When the functional group of the binder resin is a carboxyl group, examples of the curing agent include a polyepoxy compound, a polyhydroxy compound, and a β-hydroxyalkylamide compound.
Further, when the functional group of the binder resin is an epoxy group, the curing agent may be an aliphatic polycarboxylic acid such as decanedicarboxylic acid or sebacic acid, a polycarboxylic acid anhydride, dicyandiamide, a blocked isocyanate compound, or an amine-based compound. Examples thereof include a curing agent, a polyamide-based curing agent, a phenol resin, imidazoles and imidazolines. The ratio between the binder resin and the curing agent is preferably such that the functional groups involved in curing do not significantly deviate from the stoichiometrically equivalent ratio.

Examples of the silicate compound include tetraalkoxysilanes having an alkoxy group having 1 to 8 carbon atoms, condensates thereof, and compounds obtained by substituting the alkoxy groups of these condensates with alcohols. Of these, preferred are condensates of tetramethoxysilane or tetraethoxysilane, and those obtained by substituting the alkoxy group of these two condensates with an alcohol.

Specific examples of the tetraalkoxysilane having an alkoxy group having 1 to 8 carbon atoms include tetramethoxysilane, tetraethoxysilane, tetrabutoxysilane, tetrahexyloxysilane, and tetraoctyloxysilane. . In addition, the condensates of tetramethoxysilane and tetraethoxysilane listed as preferable ones were obtained from Mitsubishi Chemical Corporation as MK, respectively.
It is commercially available as the S-silicate MS series and as the ethyl silicate series from Colcoat.

In another preferred example, the alkoxy group of the condensate of tetramethoxysilane and tetraethoxysilane is substituted with an alcohol, and the alcohol is used in an amount of 1 mol or more per 1 mol of the condensate. By carrying out an exchange reaction. The amount of the above alcohol can be appropriately increased according to the number of target substituents. The exchange reaction is preferably performed by heating to, for example, about 150 ° C.
Further, in order to make the reaction proceed, it is preferable to reduce the pressure of the system and distill off the generated methanol or ethanol to the outside of the system. The reaction is terminated when a predetermined amount of substitution with alcohol has been performed. After the reaction is completed, separate
Purification can be performed to obtain a target silicate compound. The silicate compound thus obtained is
Generally, it is a colorless to pale yellow oily substance. The determination of the replacement amount with the alcohol is performed by checking the amount of the produced methanol or ethanol or by using an analytical instrument.

The alcohol used for the substitution of the alkoxy group includes propanol, butanol, benzyl alcohol, 2-butoxyethanol, 3-methoxy-
1-propanol, 2-ethylhexanol, octanol and the like can be used.

The solvent does not have to be particularly used,
When used, it is preferably 10 times or less based on the total weight of the above condensate and alcohol. Specific examples of the solvent include, for example, aromatic hydrocarbons such as toluene, benzene and xylene, halogenated hydrocarbons such as dichloroethane, ethers such as THF and dioxane,
Examples include ketones such as methyl ethyl ketone and methyl isobutyl ketone, esters such as ethyl acetate and butyl acetate, dimethyl carbonate, and acetonitrile.

In the above exchange reaction, an acid or a base can be used as a catalyst, if necessary. Examples of the acid include a Bronsted acid such as hydrochloric acid, sulfuric acid, phosphoric acid, and sulfonic acid, and a Lewis acid such as an organic tin compound.
As the base, triethylamine, dimethylbenzylamine, diazabicyclo [2.2.2. ] Octane,
1,8-diazabicyclo [5.4.0] undensen-
Tertiary amines such as 7 can be used.

The silicate compound is 0.2% based on the total resin solid content of the binder resin and the curing agent.
It is preferably from 10 to 10% by weight. If the content is less than 0.2% by weight, the content of the silicate compound in the obtained powder coating composition will be low, and a coating film having excellent stain resistance may not be obtained. On the other hand, if it exceeds 10% by weight, a problem may occur in the stability of the powder coating composition. A more preferred range is 1 to 5% by weight.

The raw material may contain a pigment in addition to the binder resin, the curing agent, and the silicate compound. As the pigment, generally used pigments can be used. Specifically, titanium dioxide,
Coloring pigments such as red iron oxide, yellow iron oxide, carbon black, phthalocyanine blue, phthalocyanine green, quinacridone pigments, azo pigments, metallic pigments, pearl pigments, metal powders and those subjected to surface treatment, talc, silica, calcium carbonate And extender pigments such as precipitated barium sulfate. The content of the pigment in the powder coating is not particularly limited, but generally, with respect to the total amount of the binder resin and the curing agent,
Preferably, the amount is 50 to 100% by weight.

The raw material may further contain other components such as a curing catalyst such as a tin compound and additives. Examples of the additive include a surface conditioner, a plasticizer, an ultraviolet absorber, an antioxidant, an anti-penetration agent, a charge control agent, and a fluidity imparting agent. These are preferably contained in such an amount that they can exhibit their functions and do not cause any trouble when added.

In the first method for producing a powder coating composition according to the present invention, it is preferable that the above-mentioned raw materials are first preliminarily mixed using a super mixer or a Henschel mixer. The raw materials are put into a kneader such as a kneader or an extruder, and the first melt-kneading is performed.
The heating temperature at this time, at least a part of the raw material is melted,
The temperature is set between a temperature at which the whole can be kneaded and a curing temperature for baking, which will be described later, and is generally in the range of 60 to 150 ° C, preferably 80 to 130 ° C. Further, it is preferable that the number of rotations is set according to the kneading condition. The melt thus obtained is once cooled and solidified by a cooling roll, a cooling conveyor, or the like, and then pulverized to a size that can be easily introduced into the kneader. The pulverized melt is again put into the kneader to perform the second melt-kneading. When the melt solidified by cooling again is repeatedly melt-kneaded, the melt is kneaded repeatedly and pulverized into a size which is easy to be put into a kneader, as in the above case. 2
The heating conditions for the subsequent melt-kneading may be changed, but need not be changed.

When the second melt-kneading is completed and further melt-kneading is to be performed, the above operation may be repeated. When no further melt-kneading is to be performed, coarse and fine pulverization steps are performed. The powder is pulverized to a desired particle size to obtain a powder coating composition. The volume average particle diameter is classified in order to remove large particles and fine particles and adjust the particle size distribution,
Preferably, it is set to 0 μm. When used for thin film coating, the thickness is more preferably set to 5 to 40 μm, and particularly to obtain a thin and smooth coating film, to 5 to 30 μm. In addition, it is preferable that the fluidity imparting agent is added after the pulverization. In this way, a powder coating composition having excellent stain resistance can be obtained.

According to the second method for producing a powder coating composition of the present invention, a second raw material containing a component capable of deactivating a silicate compound is added to a component obtained by melt-kneading a first raw material. It is characterized by kneading.

The method for producing the second powder coating composition is as follows:
First, the raw material components used for producing a powder coating material are classified into a binder resin and a silicate compound, a component in which the silicate compound is deactivated, and other components. The component that deactivates the silicate compound is not limited as long as a problem occurs when the silicate compound is brought into contact with the silicate compound such as a pigment. The description of the method for producing the first powder coating composition described above is applied to each component of the raw materials used here.

Here, the binder resin and the silicate compound are used as the first raw material, and the component that deactivates the silicate compound is used as the second raw material. The other components described above may be included in either the first raw material or the second raw material, or may be divided into appropriate amounts and included in each raw material.

In the second method for producing a powder coating composition according to the present invention, the first raw material comprising the binder resin and the silicate compound is first melt-kneaded. The heating temperature is generally 60 to 150 ° C, preferably 80 to 130 ° C.
However, when the first raw material does not contain a curing agent, the first raw material can be heated to a high temperature to such an extent that the binder resin and the silicate compound are not decomposed or volatilized. Further, it is preferable that the number of rotations is set according to the kneading condition. The melt of the first raw material thus obtained is cooled and solidified by a cooling roll, a cooling conveyor, or the like, and then pulverized to an appropriate size.
This pulverized material is put into a kneader together with the second raw material, but it is preferable that these are preliminarily mixed using a super mixer or a Henschel mixer before that. Next, a second melt-kneading is performed. The heating conditions of the melt-kneading do not need to be particularly changed. However, when the first raw material does not contain the curing agent and is kneaded at a high temperature, it is necessary to change the temperature to a temperature suitable for the one containing the curing agent. is there.

Although the melt thus obtained can be melt-kneaded again after cooling, it is usually pulverized to a desired particle size through coarse pulverization and fine pulverization steps. A powder coating composition having excellent stainability is obtained. The volume average particle diameter described in the first method for producing a powder coating composition is applied.

The powder coating composition excellent in stain resistance of the present invention is a powder coating composition obtained by the above two production methods. In the powder coating composition, the silicate compound is sufficiently kneaded into the binder resin. This is because, for example, the domain size of the silicate compound confirmed by observing the powder coating composition and the cured coating film obtained therefrom with a transmission electron microscope is smaller than that obtained by the conventional production method. Can be confirmed.

In the method for forming a coating film of the present invention, the powder coating composition obtained by the above two production methods is applied to a substrate and then baked to form a coating film having excellent stain resistance. What you get. The substrate is not particularly limited as long as it does not cause a problem such as deformation due to baking after coating, and specific examples include an iron plate, a steel plate, an aluminum plate and the like and surface-treated ones thereof. Can be. Since the coating film obtained from the enamel powder coating composition of the present invention is excellent in stain resistance, the above-mentioned base material is applied to vending machines installed outdoors, switchboards, building exterior materials and the like. preferable. In addition, an undercoating film obtained from an undercoating material such as a primer may be formed on the base material. The coating film forming method of the present invention is used to form a coating film located on the uppermost layer since a coating film having excellent stain resistance is obtained.

The method of coating is not particularly limited, and a method well known by those skilled in the art such as an electrostatic coating method and a fluid immersion method can be used. Is preferred. Examples of the charging method in the electrostatic coating method include a corona charging method and a friction charging method. These methods can be used in combination. The coating film thickness is not particularly limited.
It can be 0 to 200 μm. After application, based on the type of binder resin and curing agent contained, 1
Baking is performed at 40 to 220 ° C. for 5 to 40 minutes to obtain a coating film having excellent stain resistance.

[0034]

EXAMPLES Production Example 1 Alcohol-substituted ethyl acetate
Preparation of a silicate compound ( 1 ) 504 g of ethyl silicate 48 (condensate having an average degree of condensation of tetraethoxysilane manufactured by Colcoat Co., Ltd. of 10) was added to 504 g.
396 g of butoxyethanol and 5.06 g of triethylamine were added, and the mixture was heated and stirred at 90 ° C. for 1 hour, 120 ° C. for 2 hours, and 140 ° C. for 2 hours while removing generated ethanol. After cooling, the remaining 2-butoxyethanol was removed under reduced pressure to obtain 696 g of an ethylsilicate compound substituted with 2-butoxyethanol. The number of 2-butoxyethoxy groups in this ethyl silicate compound was 9 as determined from ¹ H-NMR.

Example 1 Clear powder coating containing silicate
Production of Composition 600 parts of Krillcoat 7642 (carboxyl group-containing polyester resin from Daicel UCB, acid value 35, weight average molecular weight 7,800, glass transition point 63 ° C.), Primid XL552 (1,1, manufactured by EMS-PRIMD)
After mixing 30 parts of 8,8-tetra (2-hydroxyethyl) adipamide), 18 parts of the ethyl silicate compound substituted with the alcohol of Production Example 1, and 5 parts of benzoin as a surface conditioner with a Henschel mixer, 100 to 1 parts were mixed.
The mixture was kneaded with a kneader while heating to 10 ° C. After cooling, pulverize to an appropriate size, knead again with a kneader while heating to 100 to 110 ° C., cool, pulverize and classify to obtain a clear powder coating composition having a volume average particle diameter of 35 μm. Obtained.

Comparative Example 1 A clear powder coating composition having a volume average particle diameter of 35 μm was obtained in the same manner as in Example 1 except that the melt kneading was performed only once.

Example 2 Silicate-containing enamel powder coating
Charge producing acrylic coating 7642 of the composition (Daicel UCB Co. carboxyl group-containing polyester resin, acid value 35, weight average molecular weight 7800, glass transition point 63 ° C.) 600 parts Primid XL552 (EMS-PRIMD Co. 1,1 ,
After mixing 30 parts of 8,8-tetra (2-hydroxyethyl) adipamide), 18 parts of the ethyl silicate compound substituted with the alcohol of Production Example 1, and 5 parts of benzoin as a surface conditioner with a Henschel mixer, 100 to 1 parts were mixed.
The mixture was kneaded with a kneader while heating to 10 ° C. After cooling, pulverize to an appropriate size, add 400 parts of CR-90 (titanium dioxide manufactured by Ishihara Sangyo Co., Ltd.), mix with a Henschel mixer, and knead again with a kneader while heating to 100 to 110 ° C. The mixture was cooled, pulverized and classified to obtain an enamel powder coating composition having a volume average particle size of 37 μm.

Comparative Example 2 An enamel powder coating composition having a volume average particle diameter of 38 μm was prepared in the same manner as in Example 2, except that all components including the pigment were mixed with a Henschel mixer and melt-kneaded only once. I got

<Evaluation of Coating Film> The powder coating materials of Examples 1 and 2 and Comparative Examples 1 and 2 were each electrostatically applied to a zinc phosphate-treated steel sheet by a corona charging type coating gun so as to have a thickness of about 60 μm. After coating and baking at 180 ° C. for 20 minutes to obtain a coating film, the gloss was measured. Further, regarding the clear coating film obtained from the powder coatings of Example 1 and Comparative Example 1,
The transparency was evaluated visually.

Next, the coating film was subjected to a humidity of 85% or more and a temperature of 5%.
After 24 hours in an environment maintained at 0 ° C., the surface water contact angle was measured using a CA-A type contact angle measuring device manufactured by Kyowa Interface Science Co., Ltd. When the angle is less than 60 degrees, the surface is sufficiently hydrophilized and has excellent stain resistance. Table 1 summarizes the obtained results.

[0041]

[Table 1]

In Example 1, since the melt-kneading was performed twice, the silicate compound was sufficiently dispersed in the binder, and there was no problem in gloss and transparency of the coating film. On the other hand, in Comparative Example 1 in which the melt-kneading was performed only once, the glossiness was low and the coating film was turbid. On the other hand, the glossiness of the coating film obtained from the powder coating material of Example 2 was good, while the glossiness of Comparative Example 2 in which the pigment was kneaded from the beginning was very poor.

[0043]

According to the method for producing a powder coating composition of the present invention, since the silicate compound is sufficiently kneaded into the binder resin, a coating film having excellent stain resistance can be obtained.
This is because in the first production method, the melt kneading is performed twice or more, and in the second production method, the binder resin and the silicate compound are first kneaded,
Each can be achieved. In particular, when a component that inactivates a silicate compound such as a pigment is contained,
Is effective because the silicate compound is first sufficiently dispersed in the binder resin to minimize the contact with the component for deactivating the silicate compound during the melt-kneading.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Nobuo Iga 19-17 Ikedanakacho, Neyagawa-shi, Osaka Nippon Paint Co., Ltd. Int Co., Ltd. F term (reference) 4J038 CG001 CG141 CG161 CG171 CH121 CH171 CH201 DB001 DB021 DB031 DB041 DB061 DB071 DB091 DB131 DB221 DD001 DL022 KA03 KA08 LA06 NA05 PA02

Claims (6)

[Claims] 1. A method for producing a powder coating composition by melt-kneading a raw material comprising a binder resin, a curing agent, and a silicate compound, wherein the melt-kneading is performed twice or more. For producing a powder coating composition having excellent heat resistance. 2. The method according to claim 1, wherein the raw material further contains a pigment. 3. A method in which a first raw material comprising a binder resin and a silicate compound is melt-kneaded, and a second raw material containing a component which deactivates the silicate compound is added to the component obtained by melt-kneading. A method for producing a powder coating composition having excellent stain resistance. 4. The method according to claim 3, wherein said deactivating component is a pigment. 5. An enamel powder coating composition obtained by the production method according to claim 1, which is excellent in stain resistance. 6. A method for forming a coating film having excellent stain resistance, wherein the powder coating composition according to claim 5 is applied and baked.